Memorandum

From: Edward Glover and Harvey Michaels

Assessment and Standards Division, Office of Transportation and Air Quality

To: Docket EPA

- HQ

- OAR

- 2011

- 0135

Subject: Sulfate

, SO2 , and OC Updates to MOVES for the Tier 3 NPRM

Date: 26 February 2013

ABSTRACT

This document describes the data and methodology used to develop the Post MOVES2010A

model sulfate, gaseous SO2 and Organic Carbon (OC) emission factors

. The gasoline vehicle

sulfate emission rates are based on 2004

- 2005 calendar year vehicle t esting done in Kansas City,

Missouri. The diesel sulfate rates for 1960 through 2006 model year diesel vehicles were taken

from predecessor model

- MOBILE6.2 because no new data were available. However, the 2007

and later model year, trap equipped vehicl es were modeled with new data collected by Southwest

Research Institute under contract with the Coordinating Research Council (CRC) as part of the

Phase 1 of the Advanced Collaborative Emissions Study (ACES)

. These data allowed for

revised modeling of SO 4, SO2 and OC emission rates in MOVES on 2007 and later model year

diesel vehicles. The gasoline vehicle sulfate rates were obtained from a least squares linear

regression of the data

.

The data and results of the analysis are shown tabular and graphic al format . The gasoline sulfat e

emission rates are 2.004e

- 07 and 1.4807e

- 08 grams SO4 / (g fuel * ppm S) for the pre

- 1981 and

1981+ model year groups, respectively. The rate is 1.37 1 e

- 07 grams SO4 / (g fuel * ppm S ) for

pre

- 2007 diesel vehicles , and 3.14 3e

- 06 grams SO4 / (g fuel * ppm S) for the 2007 and later

model years

.

The corresponding SO2 emission rates are: 2.0e

- 06 grams SO2 / (g fuel * ppm S) for gasoline

vehicles, and 1.97e

- 06 and 1.083e

- 06 grams SO2 / (g fuel * ppm S) for pre and post 2007 mo del

year diesel vehicles. Gaseous SO2 emission rates now represent 54 percent of the total fuel

sulfur (mass basis) rather than the 98 percent assumption of previous versions of MOVES.

The Organic Carbon (OC) emission rates for 2007 and later model yea r diesels were also

modified and are set equal to 1.61 times the Elemental Carbon (EC) emission rates. This value

was chosen because it leaves the Total PM2.5 unchanged for a National MOVES run in calendar

year 2040 using 11 ppm sulfur diesel fuel. Pre

- 2007 model year diesel particulate rates and

gasoline rates remain unchanged from previous MOVES versions

.

BACKGROUND and INTRODUCTIONGasoline Vehicles

Sulfate particulate matter (PM) emissions have been estimated by EPA vehicle emission

factor mod els since the development of the PART5 model in 1995. In 2002, the PART5 model

was updated with new methodologies and incorporated into the M OBILE6.2 emission factor

model (s ee EPA report EPA420

- R

- 03

- 001 “ MOBILE6.2 Particulate Emission Factor Model

Techni cal Description” for details regarding the transition from PART5 to MOBILE6.2). The

new model changed the calculation methodology by adding a fuel sulfur mass balance to the

equation. However, the update did not involve a new data collection or analysis effort

, nor did it

substantially change the sulfate PM emission factors. As a result, even the new MOBILE6.2

model is based almost entirely on data collected prior to 1995

, and most of these data consist of

tests on pre

- 1990 model year vehicles.

The PAR T5 / MOBILE6.2 (MOBILE6.2) sulfate emission factors are a function of

several detailed vehicle parameters. These are catalyst availability, catalyst type, air injection

availability, average vehicle speed over a cycle and vehicle fuel economy. The calcul ations

require three parameters: the basic sulfate emission rates (which depend on speed), the

technology weighting factors (air injection type, catalyst type, etc.), and the vehicle fuel

economy values. The basic sulfate emission factors are shown in Tab le 1. These were taken

from the PART5 model, and were not updated for MOBILE6.2. The vehicle fleet technology

weighting factors and the fuel economy values are from MOBILE6. Separate sulfate emission

factors were developed for two speed bins: 19.6 MPH an d 34.8 MPH. Sulfate emission levels at

intermediate speeds are calculated by linear interpolation between these two speeds.

All of the emission test data used in the MOBILE6.2 sulfate emission factors were

collected based on an underlying gasoline fuel s ulfur level of approximately 340 ppm sulfur

(0.034 wt%). In order to model other fuel sulfur levels, a simple linear versus fuel sulfur level

equation was constructed by assuming that a 0 ppm gasoline fuel sulfur level will produce zero

sulfate emission s (assumes no contribution from the lubricating oil). Although the effect may be

nonlinear, the linear model was also extrapolated to 1000 ppm fuel sulfur to allow estimates to

be generated for historical high sulfur fuel. The linear sulfur function was used because no data

were available to develop any other functional response.

Diesel Vehicles

No new data were available for 1960

– 2006 model year diesel vehicles so as a result, the

existing MOBILE6.2 emission rates were carried over into MOVES. For the 2007 and later

model years, a limited sample of four new, trap equipped vehicles was available for analysis

from the Coordinating Research Council (CRC) funded test program

- Advanced Collaborative

Emissions Study ( ACES). The results from this te st program suggested that the current data and

assumptions regarding sulfate (SO4), gaseous sulfur dioxide emissions (SO2) and organic carbon

(OC) formation in the presence of traps were incorrect. As a result, the emission rates for these

particulate con stituents were revised, accordingly.DATA

A new study conducted by EPA and others conducted in Kansas City, Missouri in

calendar year 2004 forms the basis of the gasoline SO4 and SO2 emission rates. In this study,

several hundred gasoline vehicles (ca rs and trucks) were recruited and tested for a range of

pollutants (HC, CO, NOx, and PM) using several test procedures. A several reports and the

complete data set are available at the link:



### http://www.epa.gov/otaq/emission

- factors

- research/index.htm

F uel sulfur measurements and sulfate emission measurements were also performed on a

subset of the vehicles. It is this limited subset of vehicles on which this analysis of vehicle

sulfate emissions is based. All of the data are shown in Table 2 entitled “Vehicle Sulfate and

Fuel Sulfur Data from the Kansas City Test Program”. It is shown at the end of this document.

In the Kansas City test program, 75 vehicles were tested for sulfate emissions, and fuel

samples from 48 vehicles were tested for fuel sulf ur levels. Unfortunately, there were only

sixteen (16) vehicles which received both the LA92 sulfate exhaust emission test and fuel

composition sulfur test measurements. Only the vehicles which received both tests were used in

the analysis. The remainin g vehicles which received only the sulfate emission test or the fuel

sulfur test were used to confirm the results.

The report entitled “CRC Report: ACES Phase 1 of the Advanced Collaborative

Emissions Study, June, 2009. Contains describes all of the instrumentation, produces and

contains the primary data collected during the study. None of this information will be repeated

in the this document. The interested reader is referred to the original documentation. It can be

obtained at the following lin k.

http://www.crcao.org/reports/recentstudies2009/ACES%20Phase%201/ACES%20P

hase1%20Final%20Report%2015JUN2009.pdf

ANALYSIS

1 .0 Sulfate Emission Calculation for Gasoline Vehicles

The gasoline vehicle test sample was divided into two strata based on model year. The

larger sample that consisted of 44 vehicles was the 1981 and later model years. A small sub

sample of 9 pre

- 1981 vehicles was also analyzed. This separation was done because of the

considerable differences in technology between the two strata, and an expected difference in the

magnitude of the sulfate emission factors.

Previous research (from PART5 model analys is) suggests significant differences in

sulfate emissions exist between vehicles with oxidation only catalysts (or no catalyst) and airinjection systems and the more modern closed loop three

- way catalysts that are typical of the

1981 and later vehicles. The differences likely arise from the different catalytic chemistry that

occurs in the oxidation

- only catalyst versus the three

- way catalysts. Also, the presence of excess

air in the older systems with air injection may allow for greater production of su lfate (SO4)

particulate versus other forms of gaseous sulfur compounds (i.e., SO2).

Model year group stratification is required in the MOVES model because specific

technology stratification by catalyst type (oxidation, three

- way, or three

- way plus oxidat ion) and

supplemental air injection presence is not available. These parameters are not included in

MOVES model because data on the frequencies of occurrence in the vehicle population of

specific vehicle technology items are usually difficult to obtain an d update in sufficient detail,

and are mostly irrelevant anyway for modern vehicles . The auto industry has long standardized

on the closed loop three

- way catalyst technology with only limited application of supplemental

air injection or other similar stra tegies. The MOVES2006 model also has a limited scope of

calendar year coverage with a focus on calendar years of 1990 through 2050.

The analysis of the vehicle sulfate data consisted of a least squares linear regression of

the sulfate emission versus the gasoline fuel sulfur levels. A regression was performed on both

the pre

- 1981 model year sample and the 1981 and later sample. The product of the regression

was a sulfate emission slope versus fuel sulfur level in units of ppm. The regression was forced

through the origin by assuming that sulfate emission will be zero at a gasoline fuel sulfur level of

zero.

Both Figures 1 and 2 were taken directly from an EPA contractor (Sierra Research) report

“Development of Emission Rates for the MOVES Model

– Ma rch 3, 2010”. These figures are

based on an updated analysis that Sierra Research performed on the full set of EPA’s Kansas

City Study data. The Original analysis done by EPA included only a sample of the full dataset

and the individual points are labele d “Original” with solid square points in Figures 1 and 2. The

additional data points are labeled “New Data” with ‘X’ points, and the regression analysis is

based on the full data sample.

A regression was performed to determine the slope of the equation:

SO 4 (g/mi) = slope × fuel S (ppm) (forcing zero intercept)Figure 1

Exhaust SO 4 vs. Fuel S

– 1981 and Newer

0.0000 0.0005 0.0010 0.0015 0.0020 0.0025

0 100 200 300 400 500

Fuel S (ppm)Exhaust SO4 (g/mi)

Original

New Data

Linear (Original)

Linear (New Data)

The newly developed combined slope was slightly more than half of that developed with

the original limited sample. This Updated slope wa s used subsequen tly in the analysis; the

Original slope was not used.

Original 0.000002952

Update 0.000001597 grams/mile SO4 / ppm fuel sulfur

Also, o nly four of the more modern vehicles had SO 4 emissions results above 0.0005

g/mi, with little response to varying sulfur level in the fuel. The average SO 4 emission rate for

this group of vehicles was 0.000344

.Figure 2

Exhaust SO 4 vs. Fuel S

– 198 0 and Older

0.0000 0.0020 0.0040 0.0060 0.0080 0.0100 0.0120 0.0140

0 50 100 150 200

Fuel SExhaust SO4- g/mi

Original

New Data

Linear (Original)

Linear (New Data)

The results obtained with 1980 and older vehicles were similar and are displayed in

Figure 2. The original analysis included only three vehicles. The slope was determined by

averaging the three Exhaust SO 4 measurements and dividing by the average fuel S for those tests.

In the updated analysis, several additional vehicle t ests were found, and a slope was determined

using linear regression.

Original 0.00002892

Update 0.00001907 grams/mile SO4 / ppm fuel sulfur

The slope developed with the combined data set for older vehicles is more than 10X the

slope obtained with t he 1981 and newer vehicles. This Updated slope was used subsequently in

the analysis; the Original slope was not used. The same factors were used for ethanol fuel, with

the assumption that the sulfur level used as an input will be the leve l measured in the diluted fuel

plus the ethanol blend used on the road, not just in the blend fuel. Lacking other information, the

same factors were used for starting, running, and extended idle.

The sulfate emission factors in units of gram/mile / ppm fuel sulfur are transformed into

MOVES model usnits of grams SO4 / (gram fuel * ppm fuel Sulfur) using Equation 1

grams SO4 / (gram fuel*ppm fuel Sulfur) = SULF * FE / Fuel Density Eq 1Where,

SULF is the sulfate emission factor in grams/mile SO4 / ppmS.

1981+ 0.000001597 grams/mile SO4 / ppm fuel sulfur

Pre

- 1981 0.00001907 grams/mile SO4 / ppm fuel sulfur

FE (fuel economy) is 13. 97 miles/gallon for Pre

- 1981 model years and 19. 31 miles/gallon for

1981+ model years. These were the mean fuel economy values for the vehicle samples in the

test program. It reflects a mixture of cars and light trucks.

Fuel Density is 2 819 grams fuel / gallon fuel for gasoline. This value is MOVES default

gasoline density.

Use of Equation 1 produces the gasoline veh icle sulfate emission factors which are found

in the MOVES database.

1981+ MY 1.597

- 06 * 19. 31 / 2819 = 1.094e

- 08 gSO4/(gfuel

- ppmS)

Pre

- 1981 1.907

- 05 * 13. 97 / 2819 = 9.457e

- 0 8 gSO4/(gfuel

- ppmS)2.0 Theoretical Maximum Sulfate Emission Rat e for Gasoline Vehicles

The theoretical maximum sulfate emission rate as calculated in EPA’s PART5 model is

used as a first step is estimating the sulfur dioxide (SO2) emission factor . This method is used

because gaseous sulfur dioxide (SO2) emissions w ere not measured as part of the EPA Kansas

City test program

. These equations are based on a mass balance of fuel sulfur (i.e., all the sulfur

contained in the fuel is exhausted as either sulfate (SO4) or SO2.), and excludes lube oil

contributions which w ere not measured.

The Sulfate Equation is shown in Equation 2.

DSulf = 13.6078 * (1.0 + Water) * FDNSTY * SWGHTD * DCNVRT / FE Eq 2

W here

Dsulf g/mi Sulfate emission factor

DCNVRT fraction fuel sulfur converted to Sulfate

FDNSTY 2857 g /gallon fuel density

FE miles/gal average fuel economy

SWGHTD 0.0344 fuel sulfur c oncentration (parts per hundred) or 344 ppm.

A typical fuel sulfur concentration prior to sulfur control.

WATER 1.2857 The weight ratio of seven water molecules to sulfa te

(7*18/ 98 = 1.2857)

Constant 13.6078 Unit conversion factor (453.592 * 3)/100. Where 3 is the

weight ratio of SO4 to sulfur. 453.592 grams per pound. A

value of 100 is to correct for the weight percent of sulfur in

SWGHTD.

For more informa tion, please see reference (EPA

- AA

- AQAB

- 94

- 2) for more details on

the PART5 and MOBILE6.2 vehicle emission data and the development of the equations.

Substituting the variables into Equation 2 and setting DCNVRT equal to 1.00 to simulate

100 percent con version of all fuel sulfur to SO4 produces a value of 0.3444 g/mi SO4 as a

theoretical maximum SO4 (MAX(SO4)) value for the 1981 and later model years. A value of

0.476 g/mi is obtained as the theoretical maximum for the 1980 and earlier model years. Th ese

values are completely theoretical because in practice less than two percent of the fuel sulfur is

converted to SO4 particulate in a gasoline vehicle

. They are used as a basis for determining

sulfur to SO4 conversion as represented by the sulfate emiss ion factors produced by Equation 1.

0.344 g/mi

= 13.6078 * (1+1.2857) * (2819/453.593) * 0.0344 * 1 /19.31 1981+ MY

0.476 g/mi

= 13.6078 * (1+1.2857) * (2819/453.593) * 0.0344 * 1 / 13.97 1980

- MYThe actual conversion of fuel sulfur into SO4 based o n the MOVES sulfate emission rates

is computed by dividing the MOVES rate by the theoretical maximum values.

SO4 Conversion

= SULF * SWGHTD (in ppm) / MAX(SO4) Eq 3

1981+ MY SO4 Conversion

= 1.597e

- 06 * 344 / 0.344

= 0.1595 %

1980

- MY SO4 Conversion

= 1.907e

- 05 * 344 / 0.476

= 1.378 %

3.0 Gaseous Sulfur Dioxide Emission Calculation for Gasoline Vehicles

The SO4 conversion percentage is used to calculate the SO2 conversion percentage using

the simple formula.

SO4 conversion + SO2 conversion

= 1.0 Eq 4

1981+ MY SO2 Conversion

= 99.85 %

1980

- MY SO2 Conversion

= 98.62 %

The values for SO2 conversion are used in the calculation of gaseous SO2 emissions.

This is done using Equation 5a

. The following algebraic steps are used in the transf ormation.

SO2 = 9.072 * FDNSTY * SWGHTD * DCNVRT SO2 / FE Eq 5a

SO2 * FE = 9.072 * FDNSTY * SWGHTD * DCNVRTSO2 Eq 5b

SO2 = Constant * FDNSTY * (SO2 Conversion) / FDNSTY* 453.592 * (1,000,000 / 100)

1.9968e

- 06

= 9.072 * 6.982 * 0.9984 / (6.98 2*453.592*10000) 1981+ MY

1.9725e

- 06

= 9.072 * 6.982 * 0.9862 / (6.982*453.592*10000) 1980

- MY

Where SO2 EF is the gaseous SO2 emission factor in units (g/mileSO2 / (g

- fuel * ppm S)

4.0 Sulfate Emission Calculation for Diesel Vehicles

The sulfate emission rates for diesel vehicles as subject to the same theoretical equations

as those used for gasoline vehicles. In case of diesel vehicles there were no data available on

pre

- 2006 model year vehicles so the theoretical equations and an assumption of low sulfate

conversion were used. However, some limited data from the CRC ACES test program on 2007

and later trap equipped vehicles were available (four vehicles and multiple tests), and these were

used to generate an alternative fuel sulfur to sulfate conversion for the new technology.Diesel Sulfate from 2006 and Earlier Vehicles

DSulf = 13.6078 * (1.0 + Water) * FDNSTY * SWGHTD * DCNVRT / FE Eq 6

Dsulf g/mi Sulfate emission factor

DCNVRT 0.02 fraction fuel sulfur converted to Sulfate

FDNSTY 6.982 lb/gallon fuel density

FE miles/gal average fuel economy

SWGHTD 0.0 500 fuel sulfur concentration (parts per hundred) or 500 ppm.

A typical fuel sulfur concentration prior to sulfur control.

WATER 1.2857 The weight ratio of seven water molecules to sulfate

(7*18/ 98 = 1.2857)

Constant 13.6078 Unit conversion factor (453.592 * 3)/100. Where 3 is the

weight ratio of SO4 to sulfur. 453.592 grams per pound. A

value of 100 is to correct for the weight percent of sulf ur in

SWGHTD.

Dsulf * FE * (1gal/6.982 lbfuel) * (1 lbfuel/453.592 gfuel)

= XConstant * SWGTD / (6.982 lb * 453.592 g)

Where

XConstant

= 13.6078*(1+Water)*FDNSTY*DCNVRT

= 4.3433

Msulfate

= XConstant / FDNSTY * 453.592*(1000000/ 100)

Msulfate = 1.37142E

- 07 g SO4 / gfuel

- ppmS

The variable Msulfate is the MOVES model sulfate emission factor for 2006 and earlier

diesel vehicles. It is in units of grams of SO4 particulate per gram fuel and per ppm fuel sulfur

. It is based the PART5 assumption of a 2 percent conversion of fuel sulfur to SO4 particulate.

Diesel Sulfate from 200 7 and Later Vehicles

The strict EPA particulate standards, as promulgated for the 2007 and later model year

diesel vehicles, has f orced the introduction of trap equipped vehicles in the in

- use fleet. Recent

testing by CRC ACES has strongly suggested that vehicles equipped with trap systems have

much higher conversions of fuel sulfur to sulfate particulate than previous technology. The data

also suggests that sulfate particulate in some cases may comprise the majority of total particulate

of less than 2.5 microns.An analysis is the available ACES data suggests a SO4 conversion of 45.84 percent

should be used on trap equipped vehic les rather than a 2 percent conversion. Substituting this

higher SO4 conversion into Equation 6 yields a MOVES diesel sulfate factor of:

Msulfate = 3.1433e

- 06 g SO4 / gfuel

- ppmS

This factor was used for all 2007 model year diesel vehicles even thoug h in the fleet

some of these vehicles may not be trap equipped due to banking and trading credits, light

- duty

applications or other factors. MOVES does not contain phase

- in fractions for such technology

and other factors.

5.0 Sulfur Dioxide Emission Cal culation for Diesel Vehicles

Diesel Sulfur Dioxide from 2006 and Earlier Vehicles

The calculation of the SO2 emission factors for diesel vehicles uses the same equation as

used for gasoline vehicles. It is repeated as Equation 7. For the 2006 and earli er vehicles the

conversion from fuel sulfur to gaseous sulfur dioxide is assumed to be 98 percent.

SO2 = 9 .072 * FDNSTY * SWGHTD * ( DCNVRT SO2 ) / FE Eq 7

SO2 g/mi SO2 emission factor

DCNVRT SO2 0.98 fraction fraction fuel sulfu r converted to SO2

FDNSTY 6.982 lbs/gallon fuel density

FE miles/gal average fuel economy

SWGHTD parts per hundred fuel sulfur concentration

WATER 1.2857 (7*18 / 98)

Constant 9.072 (453.592*2)/100

SO2 * FE * (1gal/ 6.982 lbfue l) * (1 lbfuel/453.592 gfuel) = 62.07389 * SWGHTD / (6.982 lb * 453.592 g)

MOVES SO2 = 62.0738 9 / 6.982*453.592*(1000000/100)

MOVES SO2

= 1.96003E

- 06 g SO2 / gfuel

- ppmSDiesel Sul fur Dioxide from 200 7 and Later Vehicles

The calculation of the SO2 emission factors for diesel vehicles uses Equation 7. The only

difference for the 2007 and later vehicles the conversion from fuel sulfur to gaseous sulfur

dioxide which is 54.16 percent (i.e., unity minus the SO2 conversion). Given this conversion

percentage the MOVES SO2 factor is:

MOVES SO2

= 1.0832E

- 06 g SO2 / gfuel

- ppmS

6.0 Organic Carbon Particulate Emission Factors from Trap Equipped Vehicles

New Organic Carbon (OC) particulat e emission factors for the 2007 and later model year

diesel vehicles were developed in conjunction with the new sulfate emission factors. These new

OC emission factors were developed because the new CRC ACES data suggests a much different

split between th e three principal constituents of total particulate at 2.5 microns (PM2.5) than the

split MOVES currently uses.

In MOVES total PM2.5 is the sum of organic carbon (OC), elemental carbon (EC) and

sulfate. Sulfur dioxide is not considered a particulate. T his relationship is shown

mathematically in Equation 8.

Total PM2.5

= OC + EC + Sulfate Eq 8

The development of the PREVIOUS MOVE S particulate emission rate consisted of an

analysis of real time total PM2.5 data to develop total PM2.5 emission ra tes. These were then

apportioned into EC and OC using data from other test programs. The apportionment was done

on a regulatory class and operating mode basis. Although present in the Total PM2.5 totals, and

potentially double counted in the MOVES model , the sulfate emissions were unknown and

assumed to be negligible because of the assumption of a very low (<2 percent) conversion based

on non trap equipped vehicles, and a very low fuel sulfur level (i.e., < 15 ppm sulfur). Based on

the CRC ACES study, this assumption was not correct

– even at low fuel sulfur levels. In fact,

the study strongly suggests that sulfate comprises anywhere from 30 to 60 percent of the total

PM2.5 emissions, depending on the fuel sulfur level. Thus, it was determined that th e

distribution of Total PM2.5 emissions in terms of EC, OC and sulfate were incorrect in the

MOVES model as of September, 2010.

Given the new heavy

- duty diesel test data, it was decided for MOVES model

development that at a diesel fuel sulfur level of 11 ppm, the Total PM2.5 emission level from

2007 and later model year vehicles would remain the same, EC emission rates would remain the

same and that OC emissions would be reduced at the same rate as sulfate emissions are

increased. At higher levels of die sel fuel sulfur (i.e., 15 ppm sulfur regulation limit) the Total

PM2.5 will increase as a result of this change to the MOVES model. At lower fuel sulfur levelsthe Total PM2.5 will be lower. The value of 11 ppm sulfur was chosen because it is currently

the default diesel fuel sulfur level, and it is likely close to the actual fuel sulfur level used during

vehicle certification . As a background reference, the existing MOVES 2007+ model year Total

PM2.5 emission results were derived from an analysis of he avy

- duty certification test results and

data from in

- use 1996

- 2006 model year diesel vehicles

. Mathematically, th e relationship

between Total PM2.5 and its constituents is shown in Equation 9.

Total PM2.5

= SO4 + EC + EC * OC factor Eq 9

The OC f actor was computed using a standardized National and Yearly Aggregated

MOVES run for all diesel processes (i.e., running, start and extended idle), source types and road

types. See the associated spreadsheet “DevelopmentOfTheOCFactorNational data.xls” fo r

details. The value of the OC factor was computed to be 1.61.

The default MOVES organic carbon emission rates (pollutantID = 111) were computed

for the 2007 and later model year (all regclasses

– light

- duty, light heavy, medium heavy, heavy

heavy and b uses) using Equation 10.

OC(g/hr)

= 1.61 * EC (g/hr) Eq 10

Table 1 shows the relative contribution of each particulate constituent before and after the

change to the MOVES model. The change to MOVES gives better agreement with the

experimental data in terms of sulfate emissions, but still shows differences between the two in

terms of OC and EC emission levels. The emission rates of metals are not cur rently accounted

for in MOVES, but will be in cluded in future updates.

Table 1

Relative Cont ribution of Each Particulate Constituent in MOVES

For 2007 and Later Diesel Vehicles

Particulate Constituent Old MOVES Revised MOVES ACES Study Results

Organic Carbon 88.2 % 50.5 % 32.97 %

Elemental Carbon 8.4 % 4.8 % 12.28 %

Sulfate 3.4 % 44.7% 50.68 %

Metals 4.07 %7.0 References

1. EPA Kansas City Vehicle Testing Program in 2004

- 2005 Report

2. EPA

- AA

- AQAB

- 94

- 2, “Draft User’s Guide to Part5: A Program for Calculating Particle

Emissions from Motor Vehicles”, February, 1995.

3. EPA report EPA4 20

- R

- 03

- 001 “ MOBILE6.2 Particulate Emission Factor Model

Technical Description” , January, 2003.

4. Heywood, John B. “Internal Combustion Engine Fundamentals”, 1988, page 915

5. “Coordinating Research Council (CRC) Report: ACES Phase 1 of the Advanced

C ollaborative Emissions Study, June, 2009.